反证法是初中数学难度较大的内容,也是学生进一步学习数学所必须具备的重要基础知识。用反证法证题,一般可归纳为四个步骤,即:否定结论,进行推理,导出矛盾,肯定结论。否定结论。注意把结论的反面要一一列举出来,不能有遗漏,如“不大于”的否定是“小于”或“等于”。还要注意结论的否定与结论之间必须是互斥的,如“都是”的否定应为“不都是”或“至少有一个不是”,而不是“都不是”。进行推理。要做到推理的每一步有依据。推理 Proof of evidence is a junior high school mathematics more difficult content, but also students must further study mathematics must have an important basic knowledge. With the evidence of the law, the general can be summarized in four steps, namely: negative conclusion, reasoning, derive contradictions, affirmative conclusion. Negative conclusion. Note that the negatives should be listed one by one, without omission, such as “not greater than” the negation of “less than” or “equal to”. Also note that the negation of the conclusion must be mutually exclusive with the conclusion that the negation of “all” should be “not at all” or “at least one is not” rather than “not at all.” Reasoning. There is a basis for every step of reasoning. reasoning